This invention relates to a bearing device, such as a bearing device for a vehicular wheel hub, for supporting the ends of an axle in two places, on the front end and sides thereof. More particularly, the invention relates to a bearing device of the type in which two bearings, each having a predetermined positive or negative interior clearance, are clamped and fixed in the axial direction by nuts and bolts. Angular contact roller bearings, i.e., conical roller bearings and angular contact ball bearings (hereinafter collectively called "angular contact rolling bearings") preferably are used as the two bearings for supporting the ends of the axle.
U.S. Pat. No. 4,336,641 discloses a bearing device of the type described above. FIG. 1 shows the construction of a bearing device of the type disclosed in this patent. An axle member S has a peripheral stepped portions S' on the outer periphery thereof. A housing H has peripheral stepped portions H', H" in two places on the inner periphery thereof, and two conical roller bearings B1, B2 are installed between the axle S and the housing H. The bearing B1 has an edge face on the large diameter side of an inner ring B1a. The edge face abuts a radial flat portion 51 of the peripheral stepped portion S' of the axle member S. An edge face on the large diameter side of an outer ring B1b abuts against a radial flat portion 53 of one peripheral stepped portion H' of the housing H. The bearings B1 and B2 are mounted in between the axle member S and the housing H. The bearing B2 has an outer ring B2b which abuts against a radial flat portion 54 of the other peripheral stepped portion H" of the housing.
The inner ring B2a of the bearing B2 loosely mates with the front end of the axle member S. A bolt D presses a holding plate C against an edge face on the large diameter side of the inner ring B2a. This causes the inner ring B2a to displace in the axial direction, so that both of the bearings B1 and B2 are supplied with a predetermined positive or negative interior clearance, and are fixed in the axial direction. A spacer E is inserted between the edge face at the front end of the axle member S and the holding plate C to provide the bearing with a proper clearance. The amount of the clearance may be adjusted by replacing the spacer.
To adjust the amount of the clearance by replacing the spacer E, it is necessary to try a number of spacers of different thicknesses, one after another. This adjustment is time consuming, and requires skilled efforts. Moreover, if this adjustment is made too frequently, the spacer or the threads of the bolt may be damaged, and foreign substances may become lodged in the portion where the spacer is inserted.
Another method disclosed in U.S. Pat. No. 3,326,613 eliminates the need for the holding plate. In this structure, the outer periphery at the front end of the axle member has a threaded portion therein. A nut is screwed directly into the threaded port to press an inner ring against a bearing having a predetermined interior clearance. In this case, however, the clamping pressure of the nut is not adjustable. A spring member must be inserted between the nut and the bearing, or a special spacer must be used. Thus, these adjustment techniques become more complicated as the number of parts increases, or special parts are required.